Near-field exposure method and apparatus, near-field exposure mask, and device manufacturing method

ABSTRACT

A near-field exposure method wherein a pressure difference is applied between a front face and a rear face of an elastically deformable exposure mask to cause deformation of the exposure mask in accordance with a substrate to be exposed, and to cause the exposure mask surface to follow a surface irregularity state of the substrate so that these surfaces closely contact each other, for exposure based on near field light. The method includes setting the pressure difference applied between the front and rear faces of the exposure mask at a predetermined pressure difference corresponding to a surface roughness of the substrate to be exposed.

This application is a divisional application of copending U.S. patentapplication Ser. No. 10/529,893, having a 35 U.S.C. § 371 completiondate of Oct. 17, 2005.

TECHNICAL FIELD

This invention relates to a near-field exposure method, a near-fieldexposure apparatus, a near-field exposure mask, and a devicemanufacturing method.

PRIOR ART

Increasing capacity of a semiconductor memory and increasing speed anddensity of a CPU processor have inevitably necessitated furtherimprovements in fineness of microprocessing through optical lithography.Generally, the limit of microprocessing with an optical lithographicapparatus is on an order of the wavelength of a light source used. Thus,the wavelength of a light source used in optical lithographicapparatuses has been shortened more and more, by using a nearultraviolet laser, for example, and a microprocess of a 0.1 μm order isenabled.

While the fineness is being improved in the optical lithography, inorder to assure microprocessing of 0.1 μm or narrower, there stillremain many unsolved problems such as further shortening of thewavelength of a light source, development of lenses usable in such awavelength region, and the like.

As one method for solving such a problem, U.S. Pat. No. 6,171,730proposes a near-field exposure method for performing exposure on thebasis of near field light. The method and apparatus disclosed in thisU.S. patent is very useful, and it makes a large contribution to thetechnical field to which the present invention pertains. In thisnear-field exposure method, an exposure mask being elasticallydeformable is used, and a pressure difference is applied between thefront face and the rear face of the exposure mask to cause deformationthereof with respect to a substrate to be exposed, whereby the mask andthe substrate are in close contact with each other, and whereby thesubstrate is exposed with near field light. More specifically, anelastically deformable exposure mask is supported at a sufficientlyclose distance to a substrate to be exposed and, in order to causedeformation of the mask, first the pressure in one of the spaces atopposite sides of the mask that faces a light source side is increased,as compared with the pressure in the space that faces the substrate tobe exposed. As the pressure difference between the front and rear facesof the exposure mask gradually increases due to the pressure increase,the mask is deformed, and a portion thereof swelling in a convexed shapetoward the substrate to be exposed is brought into contact with thesubstrate. As the deformation grows, the area of engagement with thesubstrate increases. The pressure is increased until the mask is broughtinto contact for the entirety of a predetermined exposure region, andthe exposure is carried out in a stage in which the mask is in contactfor the whole exposure region.

Since the mask is deformed and is gradually brought into contact withthe substrate to be exposed, as described above, it is necessary that,even if the substrate to be exposed has a surface irregularity, the maskcould be deformed to follow it, and the mask could be in close contactwith the entirety of the exposure substrate. The mask should beelastically deformable to the extent that close contact on an order notgreater than 100 nm, required for the near field exposure, can beaccomplished. In the aforementioned U.S. patent, a mask having a basematerial made from a silicon nitride thin film having a thickness of 0.1μm to 100 μm is used.

In the near-field exposure method disclosed in the aforementioned U.S.patent, if the substrate to be exposed has a surface irregularity asdescribed above, it is necessary that the mask is deformed to follow thesurface irregularity, and is brought into close contact with theentirety of the substrate. Conventionally, however, it has not yet beenmade clear that what pressure difference should be applied between thefront and rear faces of the exposure mask is an appropriate pressure forobtaining close contact suitable for the near field exposure. Also, anappropriate mask thickness for obtaining close contact suitable to thenear field exposure has not yet been made clear.

DISCLOSURE OF THE INVENTION

It is accordingly an object of the present invention to provide anear-field exposure method, a near-field exposure apparatus, anear-field exposure mask and/or a device manufacturing method, by which,for performing near field exposure while deforming an elasticallydeformable exposure mask in accordance with a substrate to be exposed,the mask can be controlled to follow the surface irregularity of thesubstrate to be exposed, such that close contact suited to the nearfield exposure can be attained.

The present invention can provide a near-field exposure method, anear-field exposure apparatus, a near-field exposure mask and a devicemanufacturing method, arranged to be described below.

Specifically, in accordance with an aspect of the present invention,there is provided a near-field exposure method wherein a pressuredifference is applied between a front face and a rear face of anelastically deformable exposure mask to cause deformation of theexposure mask in accordance with a substrate to be exposed, and to causethe exposure mask surface to follow a surface irregularity state of thesubstrate so that these surfaces are in close contact with each other,for exposure based on near-field light, characterized in that thepressure difference applied between the front and rear faces of theexposure mask is set at a predetermined pressure differencecorresponding to a surface roughness of the substrate to be exposed.

In one preferred form of this aspect of the present invention, thepredetermined pressure difference is set at a pressure difference largerthan a minimum pressure P, which is determined to satisfy equation (1)below, in relation to a maximum surface roughness w at a measurementlength a of the substrate to be exposed: $\begin{matrix}{P = {P_{m} + {E\frac{16\quad{{hw}( {{4\quad h^{2}} + {( {7 - v} )w^{2}}} )}}{3\quad{a^{4}( {1 - v} )}}}}} & (1)\end{matrix}$wherein h is a thickness of a thin-film mask base material, E is aYoung's modulus, ν is Poisson's ratio, P_(m) is a pressure differencefor roughly contacting a first substrate and a second substrate witheach other.

The predetermined pressure difference may be set at a pressuredifference larger than the minimum pressure P only when the surfaceroughness of the substrate to be exposed is greater than a reachabledepth of the near field light.

In accordance with another aspect of the present invention, there isprovided a near-field exposure apparatus for performing exposure on thebasis of near field light, the apparatus comprising means for holding athin film mask, a pressure container capable of applying pressure toapply a pressure difference between a front face and a rear face of thethin film mask, control means for controlling the pressure difference, astage for holding a substrate to be exposed, and a light source,characterized in that the control means is operable to set the pressuredifference at a predetermined pressure difference corresponding to asurface roughness of the substrate to be exposed.

In one preferred form of this aspect of the present invention, thecontrol means is operable to set the predetermined pressure differenceat a pressure difference larger than a minimum pressure P, which isdetermined to satisfy equation (1) as set forth above, in relation to amaximum surface roughness w at a measurement length a of the substrateto be exposed.

The predetermined pressure difference can be set at a pressuredifference larger than the minimum pressure P only when the surfaceroughness of the substrate to be exposed is greater than a reachabledepth of the near field light.

The exposure apparatus may further comprise measuring means formeasuring a surface roughness of the substrate to be exposed.

In accordance with a further aspect of the present invention, there isprovided a near-field exposure mask to be used in an exposure processbased on near field light, while a pressure difference is appliedbetween a front face and a rear face of an elastically deformableexposure mask, to cause deformation in accordance with a substrate to beexposed and to cause the mask to follow a surface irregularity state ofthe substrate so that these surfaces are in close contact with eachother, wherein the exposure mask comprises a transparent thin-film maskbase material and a light blocking film formed thereon, characterized inthat the thin-film mask base material has a predetermined thicknessdetermined on the basis of a surface roughness of the substrate to beexposed and a pressure difference to be applied between the front andrear faces of the mask during the exposure.

In one preferred form of this aspect of the present invention, thepredetermined thickness is set at a thickness less than a maximum filmthickness determined to satisfy equations (2a) and (2b) below:$\begin{matrix}{{w( {a,h,{\Delta\quad P}} )} = {{\frac{4\quad h^{2}}{7 - v}\frac{1}{\lbrack {R( {a,h,{\Delta\quad P}} )} \rbrack^{1/3}}} + \frac{\lbrack {R( {a,h,{\Delta\quad P}} )} \rbrack^{1/3}}{3}}} & ( {2a} ) \\{{R( {a,h,{\Delta\quad P}} )} = {{\frac{1 - v}{7 - v}\frac{81\quad a^{4}\Delta\quad P}{32\quad{hE}}} + \sqrt{{1728\quad h^{6}} + ( {\frac{1 - v}{7 - v}\frac{81\quad a^{4}\Delta\quad P}{32\quad{hE}}} )}}} & ( {2b} )\end{matrix}$wherein h is a thickness of a thin-film mask base material, E is aYoung's modulus, ν is Poisson's ratio, ΔP is an applied pressure to beapplied after the rough contact, and w is a surface roughness at ameasurement length a.

The predetermined thickness may be set at a thickness, which is lessthan a smallest value of maximum thicknesses determined in accordancewith equations (2a) and (2b) mentioned above, with reference to thosesubstrate portions, respectively, in which portions, among largestsurface roughnesses at different measurement lengths with respect to thesubstrate to be exposed, the value of roughness is greater than areachable distance of the near field light.

In accordance with a yet further aspect of the present invention, thereis provided a device manufacturing method, comprising a preparing stepfor preparing a substrate for device production, an applying step forapplying a photosensitive resist for exposure, to the substrate tothereby provide a substrate to be exposed, wherein a pressure differenceis applied between a front face and a rear face of an elasticallydeformable exposure mask to cause deformation of the exposure maskrelative to the substrate to be exposed and to cause the exposure masksurface to follow the surface irregularity state of the substrate to beexposed, so that these surfaces are in close contact with each other forexposure based on near field light, and wherein the pressure differenceto be applied between the front and rear faces of the exposure mask forthe exposure is set at a predetermined pressure difference correspondingto a surface roughness of the substrate to be exposed, a developing andetching step for performing development and etching to the substratehaving been exposed, and a process step for performing a predeterminedprocess to the substrate in accordance with a device to be produced,whereby a device is produced.

In accordance with the present invention, it is possible to provide anear-field exposure method, a near-field exposure apparatus, and anear-field exposure mask by which, when an elastically deformableexposure mask is deformed relative to a substrate to be exposed, fornear field exposure, the mask can follow the surface irregularity of thesubstrate to be exposed, so that close contact of them suitable to thenear field exposure can be accomplished. Therefore, a resist pattern canbe formed very precisely and with a good reproducibility.

These and other objects, features and advantages of the presentinvention will become more apparent upon a consideration of thefollowing description of the preferred embodiments of the presentinvention taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic and diagrammatic view of a general structure of anear-field exposure apparatus, for explaining a first embodiment of thepresent invention.

FIG. 2 is a graph for explaining the relation between mask displacementw_(c) and a disk diameter a when an applied pressure is taken as aparameter in the first embodiment of the present invention.

FIG. 3 is a schematic view of a general structure of a near-fieldexposure apparatus, for explaining a second embodiment of the presentinvention.

FIG. 4 is a graph for explaining the relation between mask displacementw_(c) and a disk diameter a in which a film thickness is taken as aparameter in a third embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will now be describedwith reference to the attached drawings. Specifically, a descriptionwill be made of first, second and third embodiments of the presentinvention, wherein, for causing an exposure mask to follow the surfaceirregularity of a substrate to be exposed to thereby obtain closecontact of them suited to the near field exposure, the pressuredifference to be applied between the front and rear faces of the mask isset at a pressure difference corresponding to the surface roughness ofthe substrate to be exposed in the first and second embodiments, whilean appropriate mask thickness is set for obtaining close contact suitedto the near field exposure in the third embodiment.

FIRST EMBODIMENT

FIG. 1 illustrates the structure of a near-field exposure apparatus, forexplaining a first embodiment of the present invention.

In FIG. 1, denoted at 109 is a light source for exposure, and denoted at104 is a thin film mask, which is elastically deformable. Denoted at 107is a substrate to be exposed, that is, a silicon wafer having a resist114 applied thereto.

The thin film mask 104 comprises a base material made from a transparentthin film such as silicon nitride, for example. A metal thin film 102(light blocking film) is formed on the base material, while beingpatterned. There is a support member 103 at the peripheral portion ofthe thin-film base material 101.

In order to produce a pressure difference between the upper and lowerfaces of the thin-film mask 104, there is a pressure container 105,which is pressure applicable and is closed by a transparent lightintroducing window 106 and the thin-film mask 104.

The pressure inside the container 105 is controlled by a pressurecontroller 110, and a valve 12 is provided to close it.

The substrate 107 to be exposed is fixed on a flat wafer holder 108 byattraction, and this wafer holder 108 is fixed on an x-y stage 113.Denoted at 111 is a surface roughness measuring system for measuringsurface roughness of the substrate to be exposed. It is operable tomeasure surface roughness at a predetermined measurement length.

Next, the sequential procedure of analysis for obtaining a predeterminedpressure difference corresponding to the surface roughness of thesubstrate to be exposed, in accordance with this embodiment, will beexplained.

First, the stage 108 is moved to place and to stop the wafer at apredetermined position.

Subsequently, by using the pressure controller 110, a positive pressureP_(m) is applied into the pressure container, to cause the mask toswell, to cause it to approximate the wafer. Here, a roughness, at ameasurement length a for the surface roughness is w, is considered.

The mask being deformed by the pressure P_(m) is lying on a recessedconcave portion of the substrate (having a depth w), such that, whilethe mask is locally in contact with minute convex portions of thesubstrate, it is not in contact with the whole surface.

Here, such a state is defined as rough contact. As a model simplifyingsuch rough contact, a model in which a circular region having a diametera is supported at an outer circumference and is planar, while on theother hand, the substrate to be exposed has a central portion beingconcave from the plane mask surface with a depth w, is used and analysisis done.

From this state, a pressure ΔP is applied to the region of the mask,having a diameter a. If the central portion of the disk having adiameter a displaces by about w, in response to the pressureapplication, it can be considered that the mask surface has a shapegenerally following the wafer surface.

Thus, if the pressure ΔP that causes such a displacement can beidentified, such a value ΔP itself or a product obtained by multiplyingit by a certain safety factor C₀ (e.g., 1.5), taking into account thedeformation in random shape, may be added to the rough contact pressureP_(m) and the result may be taken as an applied pressure during theexposure.

In this embodiment, the pressure difference ΔP applying a displacementw, such as described above, was calculated as follows. First, thedeformation shape u(r) of the thin film was examined in accordance witha finite element method, and it was confirmed that the shape accordingto equation (3) below has a good approximation to it. Here, r is thedistance from the center of the disk. $\begin{matrix}{{u(r)} = {w\frac{a^{2} - {4\quad r^{2}}}{a^{2}}}} & (3)\end{matrix}$

A bending distortion energy V corresponding to this shape can beexpressed by equation (4) below. $\begin{matrix}{V = \frac{16\quad\pi\quad{D( {1 + v} )}w^{2}}{a^{2}}} & (4)\end{matrix}$

Here, D is the flexural rigidity of the thin film, and it can be definedby equation (5) below. $\begin{matrix}{D = \frac{{Eh}^{3}}{12( {1 - v^{2}} )}} & (5)\end{matrix}$

Also, as regards the distortion energy V₁ due to elongation of thecentral surface, a calculus of variation was applied and equation (6)below was obtained. $\begin{matrix}{V_{1} = \frac{2\quad\pi\quad{D( {7 + {6v} - v^{2}} )}w^{4}}{a^{2}h^{2}}} & (6)\end{matrix}$

In this manner, by applying the principle of virtual displacement to thedistortion energy as represented by V+V¹, an equation regarding theflexure is obtainable. Solving this, equation (7a) below was obtained.In this equation, h is the thickness of the thin-film mask basematerial, E is the Young's modulus, and ν is the Poisson's ratio.Alternatively, equation (7b), additionally including a safety factor C₀,may be used. $\begin{matrix}{{\Delta\quad P} = {E\frac{16\quad{{hw}( {{4\quad h^{2}} + {( {7 - v} )w^{2}}} )}}{3\quad{a^{4}( {1 - v} )}}}} & ( {7a} ) \\{{\Delta\quad P} = {C_{0}E\frac{16\quad{{hw}( {{4\quad h^{2}} + {( {7 - v} )w^{2}}} )}}{3\quad{a^{4}( {1 - v} )}}}} & ( {7b} )\end{matrix}$

The pressure P_(m) for approximating the mask and the wafer to eachother also depends on the thickness of the base material and thematerial constant and, furthermore, it depends on the mask-to-waferdistance before the pressure application. While this quantity can bederived by calculation, the approximating action of the mask and thewafer may be monitored and, on that occasion, the quantity can beacquired at once. The pressure difference ΔP obtained from equation (3)is added to pressure P_(m) having been determined in accordance with anyone of the above-described methods, and the result is taken as alower-limit set value P_(low) for the pressure to be applied to themask. By applying a pressure not lower than the lower-limit set valueP_(low), the distance between the mask and the wafer can be reduced anda good close-contact state can be accomplished.

Here, the large surface roughness corresponds to the difference betweena maximum point of displacement and a minimum point of displacement froma reference line within a measurement length. This is a quantity whichdepends on the measurement length, and also it is a statistical valuewhich varies with wafers.

On the other hand, the displacement amount w of the mask due to thepressure application is also a quantity that depends on the diameter ofthe disk considered here, that is, the measurement length for roughness.Since each of these quantities comprises a set of a plurality ofquantities, a comparison using a graph such as shown in FIG. 2, and tobe described below, may effectively be made to choose ΔP.

First, equations (7a) and (7b) are solved with respect to w, andequations (8a) and (8b) are obtained. Equation (8b) is used for R(a, h,P) in equation (8a). By using this, as shown in FIG. 2, the displacementamount w at the mask center is plotted with reference to the diameter aof the model disk. FIG. 2 illustrates a calculation example with respectto a silicon nitride film having a thickness of 0.5 nm. $\begin{matrix}{{w_{c}( {a,h,P} )} = {{\frac{4\quad h^{2\quad}}{7 - v}\frac{1}{\lbrack {R( {a,h,P} )} \rbrack^{1/3}}} + \frac{\lbrack {R( {a,h,P} )} \rbrack^{1/3}}{3}}} & ( {8a} ) \\{{R( {a,h,P} )} = {{\frac{1 - v}{7 - v}\frac{81\quad a^{4}P}{32\quad{hE}}} + \sqrt{{1728\quad h^{6}} + ( {\frac{1 - v}{7 - v}\frac{81\quad a^{4}P}{32\quad{hE}}} )^{2}}}} & ( {8b} )\end{matrix}$

From the foregoing description, it is seen that, if the largestroughness w+3a (σ is the standard deviation of the roughness) atrespective measurement lengths under an applied pressure ΔP is smallerthan w_(c) (a, h, ΔP), the mask and the wafer can follow each other.

Further, where values of surface roughness obtained with differentmeasurement lengths are plotted in the same figure and, if all of themare included in a meshed region, then it is seen that the mask and thewafer can be brought into good contact with each other.

Although the near field light depends on the pattern of opening, sinceit can reach up to a region of tens of nanometers, near field exposurecan be carried out to a surface irregularity not larger than 10 nm, forexample, without a substantial influence. In consideration of this, thesurface roughness measurement length a is made shorter and shorter and,if there is a length with which the largest surface roughness becomesnot greater than 10 nm, then the surface roughness in a region narrowerthan that length can be disregarded, since it does not substantially andadversely affect the near field exposure.

In this embodiment, the pressure controller 110 is controlled to apply apressure difference, determined in the manner described above, betweenthe front and rear faces of the thin-film mask. Then, the valve 112 isclosed to hold the pressure. Light from the light source 109 is thenprojected onto the thin-film mask 104 through the introducing window106, whereby the resist film on the wafer 107 is exposed.

In accordance with this embodiment, wherein a pressure difference suchas described above is applied and near field exposure is carried out onthe basis of it, the mask can be deformed to follow the wafer inaccordance with a pressure corresponding to the surface roughness of thewafer. As a result, a resist pattern can be produced with goodprecision. Further, since it is no longer necessary to apply anunnecessarily large pressure difference to the mask, unnecessarydeformation of the mask can be avoided, and distortion of a pattern tobe transferred can be reduced. Thus, high pattern reproducibility can beattained.

Furthermore, in addition to the exposure process described in thisembodiment, a developing and etching process may be done to the exposedsubstrate and, thereafter, a predetermined process or processescorresponding to devices to be produced on a silicon wafer, for example,may be performed, whereby devices, such as semiconductor devices,optical devices, or quantum devices, for example, can be manufactured.

SECOND EMBODIMENT

FIG. 3 shows the structure of an exposure apparatus according to asecond embodiment of the present invention.

In FIG. 3, denoted at 211 is a light source for exposure, and denoted at204 is a thin film mask, which is elastically deformable. Denoted at 209is a substrate to be exposed, that is, a silicon wafer having a resistapplied thereto.

The thin film mask 204 comprises a base material 201 made from atransparent thin film such as silicon nitride, for example. A metal thinfilm 202 (light blocking film) is formed on the base material, whilebeing patterned. There is a support member 203 at the peripheral portionof the thin-film base material 201.

In order to produce a pressure difference between the upper and lowerfaces of the thin-film mask 204, the thin-film mask 204 and a pressurecontainer 205, as well as a container cover 206, are assembled by use ofO-rings 207 and 208. Inside of the container is a closed space, which ispressure applicable, and the inside pressure of the container iscontrolled by a pressure controller 212, and a valve 213 is provided toclose it.

The substrate 209 to be exposed is fixed, by attraction, on a flat waferholder 108, which is mounted on an x-y stage 210. The stage 210 is movedto place and stop the wafer at a predetermined position. Then, by usingthe pressure controller 212, the inside pressure of the pressurecontainer is reduced to cause the thin-film mask 204 to swell, to causeit to approximate the wafer shape.

By controlling the pressure controller 212, a pressure differencecorresponding to the surface roughness of the mask is applied betweenthe front and rear faces of the mask, in a similar manner as that in thefirst embodiment, and then the valve 213 is closed to hold the pressure.In this state, light from the light source 211 is projected onto thethin-film mask 204, whereby the resist film on the wafer 209 is exposed.

In accordance with this embodiment, wherein a pressure difference suchas described above is applied and near field exposure is carried out onthe basis of it, the mask can be deformed to follow the wafer inaccordance with a pressure corresponding to the surface roughness of thewafer. As a result, a resist pattern can be produced with goodprecision. Further, since it is no longer necessary to apply anunnecessarily large pressure difference to the mask, unnecessarydeformation of the mask can be avoided and distortion of a pattern to betransferred can be reduced. Thus, high pattern reproducibility can beattained.

THIRD EMBODIMENT

In accordance with a third embodiment of the present invention, thethickness of a near-field mask is set at a thickness appropriate forobtaining close contact suited to the near field exposure, on the basisof the surface roughness of the substrate to be exposed and of thepressure difference to be applied between the front and rear faces ofthe mask during the exposure.

Once the surface roughness of the substrate to be exposed, to be usedfor near field exposure, as well as the pressure ΔP to be applied forthe close contact, are determined, the film thickness of the thin-filmmask base material corresponding to them can be designed, in the mannerto be described below.

FIG. 4 illustrates the relationship between the mask displacement amountw_(c) and the diameter a of the model disk, wherein the maskdisplacement amount w_(c) is plotted with reference to the disk diametera. The parameter in this example is the film thickness of the thin-filmmask base material. The pressure was 10 kPa. FIG. 4 is an example of acalculation to a silicon nitride film, using equations (8a) and (8b)described with reference to the first embodiment.

If the largest roughness w+3σ (σ is the standard deviation of theroughness) at respective measurement lengths are less than w_(c) (a, h,ΔP), the mask and the wafer can follow each other. The value ofroughness corresponding to various measurement lengths are plotted inFIG. 4, and a curve that passes above all the plotted points is chosen.It is seen that, by using such a film thickness, the mask and the wafercan follow each other in response to the application of a predeterminedpressure ΔP. Namely, among aggregations of largest surface roughnesses,each being determined in relation to a few measurement lengths,equations may be referred to with respect to one or those aggregationshaving a value larger than the reachable length of the near field light,and a smallest value in the aggregation of the largest film thickness ischosen. Then, a film thickness, smaller than the so selected value, maybe designed.

Alternatively, if it is predetermined that the surface roughnessincreases, as compared with the initial state, in the latter half of aprocess involving plural times of exposure operations, for example, FIG.4, which is a plot view based on equations (8a) and (8b) may be referredto and the mask thickness to be used in the first half of the processand the mask thickness to be used in the second half of the process maybe made different from each other.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide anear-field exposure method, a near-field exposure apparatus, anear-field exposure mask and/or a device manufacturing method, by which,for performing near field exposure while deforming an elasticallydeformable exposure mask in accordance with a substrate to be exposed,the mask can be controlled to follow the surface irregularity of thesubstrate to be exposed, such that close contact suited to the nearfield exposure can be attained.

While the invention has been described with reference to the structuredisclosed herein, it is not confined to the details set forth and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

This application claims priority from Japanese Patent Application No.2003-290164, filed Aug. 8, 2003, which is hereby incorporated byreference.

1. A near-field exposure method wherein a pressure difference is appliedbetween a front face and a rear face of an elastically deformableexposure mask to cause deformation of the exposure mask in accordancewith a substrate to be exposed and to cause the exposure mask surface tofollow a surface irregularity state of the substrate so that thesesurfaces are in close contact with each other, for exposure based onnear field light, said method comprising: setting the pressuredifference applied between the front and rear faces of the exposure maskat a predetermined pressure difference corresponding to a surfaceroughness of the substrate to be exposed.
 2. (canceled)
 3. (canceled) 4.A near-field exposure apparatus for performing exposure on the basis ofnear field light, said apparatus comprising means for holding a thinfilm mask; a pressure container capable of applying pressure to apply apressure difference between a front face and rear face of the thin filmmask; control means for controlling the pressure difference; a stage forholding a substrate to be exposed; and a light source, wherein saidcontrol means is operable to set the pressure difference at apredetermined pressure difference corresponding to a surface roughnessof the substrate to be exposed.
 5. (canceled)
 6. (canceled)
 7. Anapparatus according to claim 4, further comprising measuring means formeasuring a surface roughness of the substrate to be exposed.
 8. Anear-field exposure mask to be used in an exposure process based on nearfield light while a pressure difference is applied between a front faceand a rear face of an elastically deformable exposure mask to causedeformation in accordance with a substrate to be exposed and to causethe mask to follow a surface irregularity state of the substrate so thatthese surfaces are closely contacted to each other, said exposure maskcomprising: a transparent thin-film mask base material; and a lightblocking film formed therein, wherein the thin-film mask base materialhas a predetermined thickness determined on the basis of a surfaceroughness of the substrate to be exposed and a pressure difference to beapplied between the front and rear faces of the mask during theexposure.
 9. (canceled)
 10. (canceled)
 11. A device manufacturingmethod, comprising: a preparing step for preparing a substrate fordevice production; an applying step for applying a photosensitiveresist, for exposure, to the substrate to thereby provide a substrate tobe exposed; an exposure step wherein a pressure difference is appliedbetween a front face and a rear face of an elastically deformableexposure mask to cause deformation of the exposure mask relative to thesubstrate to be exposed and to cause the exposure mask surface to followthe surface irregularity state of the substrate to be exposed, so thatthese surfaces are in close contact with each other for exposure basedon near field light, and wherein the pressure difference to be appliedbetween the front and rear faces of the exposure mask for the exposureis set at a predetermined pressure difference corresponding to a surfaceroughness of the substrate to be exposed; a developing and etching stepfor performing development and etching to the substrate having beenexposed; and a process step for performing a predetermined process tothe substrate in accordance with a device to be produced, whereby adevice is produced.